Volumetric heating in coronal streamers

1996 ◽  
Vol 101 (A9) ◽  
pp. 19957-19966 ◽  
Author(s):  
S. T. Suess ◽  
A.-H. Wang ◽  
S. T. Wu
Keyword(s):  
Volumetric Heating ◽  
Coronal Streamers

Simulation of volumetric heating of a moist medium with allowance for fluid mobility

2012 ◽  
Vol 9 (1) ◽  
pp. 91-93
Author(s):  
U.R. Ilyasov ◽  
A.V. Dolgushev
Keyword(s):  
Mass Transfer ◽  
Porous Medium ◽  
Numerical Solution ◽  
Heat And Mass Transfer ◽  
Transfer Process ◽  
Thermal Action ◽  
Mass Transfer Process ◽  
Low Permeability ◽  
Volumetric Heating ◽  
Drying Regime

The problem of volumetric thermal action on a moist porous medium is considered. Numerical solution, the influence of fluid mobility on the dynamics of the heat and mass transfer process is analyzed. It is established that fluid mobility leads to a softer drying regime. It is shown that in low-permeability media, the fluid can be assumed to be stationary.

scholarly journals Microwave-Assisted Preparation of Luminescent Inorganic Materials: A Fast Route to Light Conversion and Storage Phosphors

Molecules ◽  
2021 ◽  
Vol 26 (10) ◽  
pp. 2882
Author(s):  
José Miranda de Carvalho ◽  
Cássio Cardoso Santos Pedroso ◽  
Matheus Salgado de Nichile Saula ◽  
Maria Claudia França Cunha Felinto ◽  
Hermi Felinto de Brito
Keyword(s):  
Rapid Heating ◽  
Inorganic Materials ◽  
Rapid Screening ◽  
Conventional Heating ◽  
Quantum Yields ◽  
Microwave Assisted Synthesis ◽  
Volumetric Heating ◽  
White Leds ◽  
Microwave Assisted ◽  
And Storage

Luminescent inorganic materials are used in several technological applications such as light-emitting displays, white LEDs for illumination, bioimaging, and photodynamic therapy. Usually, inorganic phosphors (e.g., complex oxides, silicates) need high temperatures and, in some cases, specific atmospheres to be formed or to obtain a homogeneous composition. Low ionic diffusion and high melting points of the precursors lead to long processing times in these solid-state syntheses with a cost in energy consumption when conventional heating methods are applied. Microwave-assisted synthesis relies on selective, volumetric heating attributed to the electromagnetic radiation interaction with the matter. The microwave heating allows for rapid heating rates and small temperature gradients yielding homogeneous, well-formed materials swiftly. Luminescent inorganic materials can benefit significantly from the microwave-assisted synthesis for high homogeneity, diverse morphology, and rapid screening of different compositions. The rapid screening allows for fast material investigation, whereas the benefits of enhanced homogeneity include improvement in the optical properties such as quantum yields and storage capacity.

Study of color kinetics of banana (Musa cavendish) under microwave drying by application of image analysis

2020 ◽  
pp. 108201322098133
Author(s):  
Sagar Nagvanshi ◽  
Subbarao Kotra Venkata ◽  
TK Goswami
Keyword(s):  
Microwave Power ◽  
Vision System ◽  
Power Level ◽  
Microwave Drying ◽  
Slice Thickness ◽  
Order Kinetic ◽  
Drying Time ◽  
Volumetric Heating ◽  
Kinetics Of ◽  
Microwave Power Level

Microwave drying works on the volumetric heating concept promoted by electromagnetic radiation at 0.915 or 2.450 GHz. In this study, banana ( Musa Cavendish) was taken as the sample and treated under microwave drying. The effect of two process variables, namely slice thickness (2, 3.5, and 5 mm) and microwave power (180 W, 360 W, and 540 W), were studied on drying kinetics and color kinetics. It was observed that the inverse variation relationship exists between drying time and microwave power level while drying time and slice thickness exhibited a direct variation relationship. A Computer Vision System (CVS) was developed to measure the color values of banana in CIELab space using an algorithm written in MATLAB software. Once the color parameters were obtained, they were fitted in First and Zero-order kinetic models. Both models were found to describe the color values adequately. This study concludes that microwave drying is a promising dehydration technique for banana drying that reduces the significant time of drying. Application of CVS is an excellent approach to measure the surface color of banana.

Natural convection in porous media: effect of weak dispersion on bifurcation

1990 ◽  
Vol 216 ◽  
pp. 285-298 ◽  
Author(s):  
Xiaowei S. He ◽  
John G. Georgiadis
Keyword(s):  
Effective Conductivity ◽  
Horizontal Layer ◽  
Hydrodynamic Dispersion ◽  
The Novel ◽  
Media Effect ◽  
Boussinesq Model ◽  
Weakly Nonlinear ◽  
Volumetric Heating ◽  
Pitchfork Bifurcations ◽  
The Impact

We use weakly nonlinear analysis via a two-parameter expansion to study bifurcation of conduction into cellular convection of an internally heated fluid in a porous medium that forms a horizontal layer between two isothermal walls. The Darcy–Boussinesq model of convection is enhanced by including two nonlinear terms: (i) quadratic (Forchheimer) drag; and (ii) hydrodynamic dispersion enhancement of the thermal conductivity described by a weak linear relationship between effective conductivity and local amplitude of filtration velocity. The impact of the second term on the shape of the bifurcation curve for two-dimensional rolls is profound in the presence of uniform volumetric heating. The resulting bifurcation structure is unlike any pitchfork bifurcations typical of the classical Bénard problem. Although direct experimental validation of the novel bifurcation is not available, we would like to register it as an alternative or a supplement to models of small imperfections, and as an attempt to account for the scatter of observed critical values for the first bifurcation.

A volumetrically heated jet: large-eddy structure and entrainment characteristics

1996 ◽  
Vol 325 ◽  
pp. 303-330 ◽  
Author(s):  
G. S. Bhat ◽  
R. Narasimha
Keyword(s):  
Large Scale ◽  
Laser Doppler Anemometry ◽  
Local Heating ◽  
Integral Model ◽  
Volumetric Heating ◽  
Electrically Conducting ◽  
Cloud Development ◽  
Entrainment Process ◽  
Centreline Velocity ◽  
Heat Injection

We report here an experimental study of a round vertical liquid jet that, after achieving a self-preserving state, is subjected to volumetric heating between two diametral stations. The heat injection is achieved by applying a voltage across the stations, the jet fluid having been rendered electrically conducting by the addition of acid. Using laser-induced fluorescence, digital image processing and laser-Doppler anemometry, the flow properties of the jet have been studied in detail. It is found that, with sufficient heating, the jet no longer grows linearly with height, and the decay of both centreline velocity and turbulence intensity is arrested, and may even be reversed just beyond the zone of heat addition; nevertheless the entrainment decreases, which is at variance with the hypotheses often made for modelling it. This behaviour is here attributed to the disruptive influence that, as the present experiments show, the volumetric heating has on the large-scale vortical structures in the jet, which are known to be largely responsible for the engulfment of ambient fluid that is the first step in the entrainment process. It is shown that a new non-dimensional heat release number correlates the observed data on changes in jet width. An integral model that would describe the effect of local heating is proposed, and implications for cloud development in the atmosphere are discussed.

Magnetic configuration of coronal streamers and threads

1994 ◽  
Vol 70 (1-2) ◽  
pp. 283-288 ◽  
Author(s):  
S. Koutchmy ◽  
V. A. Koutvitsky ◽  
M. M. Molodensky ◽  
L. S. Solov'iev ◽  
O. Koutchmy
Keyword(s):  
Magnetic Configuration ◽  
Coronal Streamers

scholarly journals Onset of Thermal Instabilities in the Plane Poiseuille Flow of Weakly Elastic Fluids: Viscous Dissipation Effects

Fluids ◽  
2021 ◽  
Vol 6 (12) ◽  
pp. 432
Author(s):  
Silvia C. Hirata ◽  
Mohamed Najib Ouarzazi
Keyword(s):  
Linear Stability ◽  
Viscous Dissipation ◽  
Viscoelastic Fluid ◽  
Poiseuille Flow ◽  
Hydrodynamic Instability ◽  
Plane Poiseuille Flow ◽  
Volumetric Heating ◽  
Fluid Elasticity ◽  
Different Temperatures ◽  
Elastic Fluids

The onset of thermal instabilities in the plane Poiseuille flow of weakly elastic fluids is examined through a linear stability analysis by taking into account the effects of viscous dissipation. The destabilizing thermal gradients may come from the different temperatures imposed on the external boundaries and/or from the volumetric heating induced by viscous dissipation. The rheological properties of the viscoelastic fluid are modeled using the Oldroyd-B constitutive equation. As in the Newtonian fluid case, the most unstable structures are found to be stationary longitudinal rolls (modes with axes aligned along the streamwise direction). For such structures, it is shown that the viscoelastic contribution to viscous dissipation may be reduced to one unique parameter: γ=λ1(1−Γ), where λ1 and Γ represent the relaxation time and the viscosity ratio of the viscoelastic fluid, respectively. It is found that the influence of the elasticity parameter γ on the linear stability characteristics is non-monotonic. The fluid elasticity stabilizes (destabilizes) the basic Poiseuille flow if γ<γ* (γ>γ*) where γ* is a particular value of γ that we have determined. It is also shown that when the temperature gradient imposed on the external boundaries is zero, the critical Reynolds number for the onset of such viscous dissipation/viscoelastic-induced instability may be well below the one needed to trigger the pure hydrodynamic instability in weakly elastic solutions.

Study of Surface and Volumetric Heating Effects in a Mach 5 Flow

2004 ◽  
Author(s):  
James Menart ◽  
Sean Henderson ◽  
Joseph Shang ◽  
Roger Kimmel ◽  
Jim Hayes ◽  
...  
Keyword(s):  
Volumetric Heating ◽  
Heating Effects
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